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排序方式: 共有137条查询结果,搜索用时 486 毫秒
21.
Vankrunkelsven S Clicq D Cabooter D De Malsche W Gardeniers JG Desmet G 《Journal of chromatography. A》2006,1102(1-2):96-103
The present paper reports on the separation of a mixture of fluorescein isothiocyanate-labeled angiotensin I and II peptides in a shear-driven nanochannel with a C18-coating and using an eluent consisting of 5% acetonitrile in 0.02 M aqueous phosphate buffer at pH 6.5. The flat-rectangular nanochannel in fused silica consisted of an etched structure in combination with a flat moving wall. The very fast separation kinetics that can be achieved in a nanochannel allowed to separate the angiotensin peptides in less then 0.2 s in a distance of only 1.8 mm. Plate heights as small as 0.4 microm were calculated after substraction of the injection effect. 相似文献
22.
Microscopic study of polymorphism of a photographic coupler 总被引:1,自引:0,他引:1
Polymorphism and polymorphic transformation of a photographic coupler have been examined using hot stage optical microscopy (HSOM). Two different polymorphs, metastable needle-like crystals and stable cubic-like crystals, were identified on heating. A solid-state transformation was found to occur from the metastable form to the stable form. Both polymorphs can precipitate from coupler solutions. The needle-like crystals appear in all cases examined; the cubic-like crystals precipitate only with higher concentrations and lower cooling rates. The solution-mediated transformation occurs in an organic solvent through dissolution of the metastable polymorph and growth of the stable polymorph. The growth rate of the stable polymorph is dependent on temperature as well as concentration. The activation energy of the growth is estimated for coupler solutions with different concentrations. 相似文献
23.
The volatile intermediate Et3NBH3 was isolated during the thermolysis of Et4NBH4 at 185°C for 16 hr under dynamic vacuum. The rate of decomposition of Et4NBH4 was studied. Separate thermolyses of Et4NBH4 (or Et3NBH3) with closo B9H92?nido B9H?12, or arachno B9H14? did not produce B10H102? as the major product. These results are inconsistent with the “build-up” mechanism previously proposed for the thermolytic convertion of BH 4? to B10H102? and a new mechanism is required. 相似文献
24.
25.
We investigate a large sample approach for obtaining tolerance bounds where the underlying population is a three-parameter Weibull distribution. Accurate tolerance bounds could play an important role in the development of lumber standards. Properties of the maximum likelihood based approach are compared with those of the standard nonparametric tolerance procedure. The asymptotic normal approximation to the tolerance bound was found to be inadequate for most of the cases considered. 相似文献
26.
27.
Klaus Bernauer Helen Stoeckli-Evans Deirdre Hugi-Cleary Hermann J. Hilgers Habib Abd-el-Khalek Joëlle Porret Jean-Jacques Sauvain 《Helvetica chimica acta》1992,75(7):2327-2339
The syntheses and characterization of four new linear pentadentate ligands and their CoIII complexes are described: N,N′-[(pyridine-2,6-diy)bis(methylene)]bis[sarcosine] (sarmp), N,N′-[(pyridine-2,6-diyl)bis(methylene)]bis[(R)- or (S)-proline] ((R,R)- or (S,S)-promp), N,N′-[(pyridine-2,6-diyl)bis(methylene)]bis[N-(methyl)-(R)- or (S)-alanine] ((R,R)- or (S,S)-malmp); 2,2′-[pyridine-2,6-diyl]bis[(S)- or rac-N-(acetic acid)pyrrolidine] ((S,S)- or rac-bapap). The complexes were characterized and, with but one exception, complex formation is stereospecific: Δ-exo-(R,R) (or Λ-exo-(S,S)) for promp and Λ-(R,R) (or Δ-(S,S)) for bapap. The exception is [Co((R,R)- or (S,S)-malmp)H2O]ClO4 for which two forms are obtained, to which Λ-endo-(R,R) (or Δ-endo-(S,S)) and, tentatively, Δ-unsymmetric-(R,R)- (or Λ-unsymmetric-(S,S)-) configurations are assigned. X-Ray crystal structures are presented for the complexes [Co(sarmp)H2O]ClO4, [Co((S,S)-promp)H2O]ClO4, [Co(rac-bapap)H2O]ClO4 and endo-[Co(rac-malmp)H2O]ClO4. Ligand acid dissociation and CoII and FeII complex-formation constants are reported. 相似文献
28.
Oligonucleotide-gold nanoparticle conjugates are employed to demonstrate selective colorimetric discrimination of a cystic fibrosis-related genetic mutation in a model oligonucleotide system. Specifically, three strand oligonucleotide complexes are employed, wherein two probe oligonucleotide-gold nanoparticle conjugates are linked together by a third target oligonucleotide strand bearing the chosen CF-related mutation. By monitoring the solution optical absorption behaviour of the complexes as a function of temperature, melting profiles may be accurately acquired and reproducibly compared. Following this method, fully complementary sequences are successfully distinguished from mismatched sequences, with single base mismatch resolution, for the V232D mutation. To extend the detection sensitivity of this oligonucleotide-nanoparticle conjugate assay, a novel and compact LED-based optical monitoring system capable of sub-picomole level colorimetric SNP discrimination is also demonstrated. 相似文献
29.
Rapid cloning and expression of a fungal polyketide synthase gene involved in squalestatin biosynthesis 总被引:7,自引:0,他引:7
Cox RJ Glod F Hurley D Lazarus CM Nicholson TP Rudd BA Simpson TJ Wilkinson B Zhang Y 《Chemical communications (Cambridge, England)》2004,(20):2260-2261
PCR primers designed to selectively amplify the unique C-methyltransferase domain of fungal polyketide synthases were used to selectively clone a polyketide synthase gene involved in the biosynthesis of the squalene synthase inhibitor squalestatin S1 , heterologous expression of which led to the biosynthesis of the squalestatin side-chain. 相似文献
30.
M. W. Hunter R. Dykstra M. H. Lim T. G. Haskell P. T. Callaghan 《Applied magnetic resonance》2009,36(1):1-8
We report on the use in Antarctica of a portable nuclear magnetic resonance spectrometer which utilizes the Earth’s magnetic
field. We obtain estimates of brine content, in samples of sea ice extracted at different depths from the annual ice of McMurdo
Sound, in the vicinity of Cape Evans, Ross Island. These measurements are correlated with estimates of brine content obtained
from temperature and salinity measurements at each depth, using a knowledge of the phase diagram. 相似文献